harjp

I paid $485 to a great local indie exhaust shop for two Flowmaster cats installed plus two new O2 sensors.

Well, it was the cats after all. New cats dropped the NOx emissions from just above 2.50 g/mile to 0.77. Not sure why mine got "used up" with less than 120K on the car. Oh well. I know there are ways around it, but I wanted the car to be in good working order and emissions complaint.

One of the things I was looking for in this thread was whether LS400 owners with 100K+ on their cars have had to replace their cats. If they don't last for 200K miles, then I'd expect to hear from others who have had to replace them by now.

Oh, OK. Thanks. I'll try that. I checked the emissions results from 2 years ago. The NOx reading was 1/2 of what it is now. What I didn't mention above was that on the first try, the NOx reading was over 8.0. It looked like the EGR vacuum modulator was not working right, so I by-passed it, running a hose from one of the intake manifold vacuum ports straight to the EGR valve. That brought the reading down to just above the standard. I just picked up a new EGR VM. Maybe that will make the difference. I find it difficult to believe my cats are spent.

The shop is run by a state agency. They do a few runs to try and pass you, but it's setup to eliminate any discretion: pass or fail is determined by the computer. I'd love to give that a try. I use full throttle for seconds at a time whenever I can. Yes -- because it's fun. I sometimes run with the overdrive off, or even run the car in 2nd gear, because that's the only way to get the RPMs up for any length of time and the throttle response is great. But full throttle for a "few minutes"? I can't think of anywhere I could go that fast around here. And even if I could, I have to admit I don't have the balls to run at 100+ mph on public highways. I don't mind getting the cats replaced if that means I'm definitely going to pass emissions. My only concern is to spend the $$$ only to find that the cats weren't the problem!

My '90 LS400 won't pass emissions this year, after 3 tries. NOx just misses the standard. The standard is 2.50 g/mile. My car produced 2.53 and 2.58 last two tries. EGR is not the problem (so I'm told). Tried Seafoaming a couple of times to make sure the valves are free. Only thing left to do, it seems, is replace the catalytic converters. Cats are not plugged, but possibly used up? Would like to hear from others who found themselves in this situation. I'd hate to replace the cats and still fail emissions.

By the way, the lexls.com tutorial on the timing belt includes changing the water pump. http://www.lexls.com/tutorials/engine/timingbelt.html Is that something that ought to be done when you do the timing belt? Also, what are idler pulleys and why do you need new ones? What a lot of work and expense to replace a $50 belt!

In "high-speed idling" the car over to the mechanic last night, the engine would run OK for a bit and then refuse to rev up. And in doing so, I go the distinct impression that something was slipping under the hood. So now I think chilkoot called it right from the start -- the timing belt. Would a worn and slipping timing belt cause the engine to surge at idle because the cams are basically unregulated? (As for my thinking the timing belt had been changed at 90K, that may have been wishful remembering....)

I read somewhere else in this forum that "surging" can be caused by a bad TPS. Any thoughts on that? After starting, and even though surging, the engine is running very smoothly -- not rough or anything. When I turn the A/C on, the surging stops. But then, as I said, when in gear and I give the engine gas, it won't build RPM. If in neutral, it will rev up.

No sudden jolts. Don't believe it's the timing belt. It was replaced at 90K and the car has (mostly) run fine since then. About 3-4 weeks since I seamfoamed the engine.

Hi. I'm stumped and almost ready to give up on my 1990 LS400. Car has 115K miles on it and has recently seen some problems. First the MAF meter went and I installed a remanufactured one. That cured the sluggishness and eliminated the CEL. Still had the low idle problem though, so I cleaned the throttle body and Seafoamed the engine. That helped a lot -- idle speed was up, though still on the low side. But overall, the car ran great. Then, just a few days ago, the engine started surging when I started the car. Oscillates between 650 and 1200 rpm. I replaced the fuel filter, cleaned the idle air control valve, and cleaned and adjusted the TPS. Today when I went to drive it, the car continued to surge and rev high when I started it, but now it stumbles badly when I apply throttle. No CEL. But if I try and give it any gas at all, it totally bogs. Can't get the rpm's to come up at all. I'm very disappointed that I seem to be making the car run worse, not better. Any idea what's going on? Thanks.

Changed the oil today after putting about 50 miles on the car following the Seafoam treatment. Old oil was very thin and very dirty. Regular Jiffy Lube dino with about 4000 miles on it. Came out almost like water, but nearly black. Changed it myself this time. Went with some nice Mobil 1 full synth. Also replaced the PCV valve. Car is running much better. Definitely more responsive. Think the air/fuel table isn't where it needs to be yet, but getting there. Idle is coming up. No more "wants to die" issues.

Do you know if these come with new ball joints? Where'd you get those from, SK?

After reading through this entire thread, I did my first Seaform to the LS400 today. I ran my car with a bad MAF meter for the last few months. Finally replaced it today. While I had it off, removed the throttle body and cleaned out the engine side. Very dirty, heavy carbon deposits. Peeked into the intake manifold and it was a mess in there too. With the new MAF on, CE light was dark for the first time in the longest time. But after some highway driving, the car stalled at a light. After that, engine wanted to die at low rpm's. I'm guessing that the car has been running rich for a while now and it will take a little while for the a/f mixture table to adjust. In the meantime, put one pint of Seafoam in the gas tank, a bit more than a 1/3 of a pint I sucked into the intake manifold using the hose that ran from the PVC valve, and dumped the rest of the second pint into the crankcase. I was very impressed by the amount of white smoke the car produced! I'll change the oil in a couple of days. Time for new oil anyway. And then I'll repeat the engine application of Seafoam a couple of times over the next few months. Just knowing how much gunk is being dissolved makes me very happy on behalf of my car. Thanks for directing me to Seafoam.

I noticed mine drooping, so I removed it and threw it away. As I did the misc. plastic under the hood that cover up the word "Toyota" on the radiator.